Un poco:  A little.

Una corda:  Soft pedal.

Unison:  Singing or playing the same notes by all singers or players, either at exactly the same pitch or in a different octave.

Upbeat:  One or more notes occurring before the first bar line, as necessitated by the text for the purpose of desirable accent. The unaccented beat of a measure.

Variation:  The manipulation of a theme by the use of melodic, rhythmic, and harmonic changes.

Vibrato:  Repeated fluctuation of pitch.

Virtuoso:  A brillant, skillful performer.

Vivace:  Lively

Vivace:  Lively, brisk, quick, and bright.

Vivo:  Lively, bright.

Volti subito:  Turn [the page] quickly.

Whole note/rest:  A note/rest equal to two half notes and four quarter notes.

Wind instrument family:  Instruments in which sound is produced by the vibration of air, including brass and woodwind instruments.